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BIG PHYSICS, BIG QUESTIONS –

Tethered satellites could see the moon’s weird swirls up close

Mystery swirls on the lunar surface

NASA

By Leah Crane

A satellite on a leash could help us learn about strange bright patterns on the moon’s surface. By connecting two small CubeSats with a tether 180 kilometres long, NASA researchers hope to put one of them in an orbit close enough to the surface to investigate the swirling patterns that show up in more than 100 places across the moon.

Lunar swirls are bright, sinewy features that look like coils of relatively pristine dust blown over the surface of the moon. They’re associated with areas of strangely strong magnetic field, whereas most of the moon has no magnetic field at all.

We’ve known about lunar swirls since the late 1970s, but nobody is quite sure what they are or how they got there. A leading theory is that these bright areas could have been preserved over time by magnetic fields which shield the whorls from charged particles in solar wind and other space weather. But it’s unclear where the magnetic fields themselves came from.

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“There’s been a lot of work on how these magnetic anomalies appear to be protecting the surface from space weather,” says Georgiana Kramer at the Lunar and Planetary Institute in Texas. “A big question is what’s causing them. Why are they there?”

Up close and personal

It’s been difficult to get an up close look at them, because an orbiter near the surface would have to be traveling extremely quickly to avoid being sucked down by the moon’s gravity and shattering in a crater.

Small satellites like these can’t carry enough fuel to move fast enough to avoid gravitational demise and maintain a low orbit, but what they can carry is enough to keep a higher orbit.

The proposal would have the two satellites shoot away from one another once they get to the moon, one toward the surface and the other out to space until the tether is taut. During the year they’re in orbit, the upper satellite would oppose the gravitational pull of the moon and keep the lower one from ending as its own strange smear on the surface.

In addition to looking at lunar swirls and their magnetic fields up close, BOLAS will examine what’s known as the moon’s hydrogen cycle in which micrometeorites and the solar wind deposit hydrogen on the surface, which then puffs the hydrogen back up.